From: Toshi Kani <toshi.kani@hp.com>
To: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
linux-acpi@vger.kernel.org, Wen Congyang <wency@cn.fujitsu.com>,
Wen Congyang <wencongyang@gmail.com>,
isimatu.yasuaki@jp.fujitsu.com, lenb@kernel.org,
gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [RFC PATCH v3 3/3] acpi_memhotplug: Allow eject to proceed on rebind scenario
Date: Thu, 29 Nov 2012 10:56:30 -0700 [thread overview]
Message-ID: <1354211790.26955.443.camel@misato.fc.hp.com> (raw)
In-Reply-To: <20121129113030.GB639@dhcp-192-168-178-175.profitbricks.localdomain>
On Thu, 2012-11-29 at 12:30 +0100, Vasilis Liaskovitis wrote:
> On Thu, Nov 29, 2012 at 11:03:05AM +0100, Rafael J. Wysocki wrote:
> > On Wednesday, November 28, 2012 06:15:42 PM Toshi Kani wrote:
> > > On Wed, 2012-11-28 at 18:02 -0700, Toshi Kani wrote:
> > > > On Thu, 2012-11-29 at 00:49 +0100, Rafael J. Wysocki wrote:
> > > > > On Wednesday, November 28, 2012 02:02:48 PM Toshi Kani wrote:
> > > > > > > > > > > > > Consider the following case:
> > > > > > > > > > > > >
> > > > > > > > > > > > > We hotremove the memory device by SCI and unbind it from the driver at the same time:
> > > > > > > > > > > > >
> > > > > > > > > > > > > CPUa CPUb
> > > > > > > > > > > > > acpi_memory_device_notify()
> > > > > > > > > > > > > unbind it from the driver
> > > > > > > > > > > > > acpi_bus_hot_remove_device()
> > > > > > > > > > > >
> [...]
> > Well, in the meantime I've had a look at acpi_bus_hot_remove_device() and
> > friends and I think there's a way to address all of these problems
> > without big redesign (for now).
> >
> > First, why don't we introduce an ACPI device flag (in the flags field of
> > struct acpi_device) called eject_forbidden or something like this such that:
> >
> > (1) It will be clear by default.
> > (2) It may only be set by a driver's .add() routine if necessary.
> > (3) Once set, it may only be cleared by the driver's .remove() routine if
> > it's safe to physically remove the device after the .remove().
> >
> > Then, after the .remove() (which must be successful) has returned, and the
> > flag is set, it will tell acpi_bus_remove() to return a specific error code
> > (such as -EBUSY or -EAGAIN). It doesn't matter if .remove() was called
> > earlier, because if it left the flag set, there's no way to clear it afterward
> > and acpi_bus_remove() will see it set anyway. I think the struct acpi_device
> > should be unregistered anyway if that error code is to be returned.
> >
> > [By the way, do you know where we free the memory allocated for struct
> > acpi_device objects?]
> >
> > Now if acpi_bus_trim() gets that error code from acpi_bus_remove(), it should
> > store it, but continue the trimming normally and finally it should return that
> > error code to acpi_bus_hot_remove_device().
>
> Side-note: In the pre_remove patches, acpi_bus_trim actually returns on the
> first error from acpi_bus_remove (e.g. when memory offlining in pre_remove
> fails). Trimming is not continued.
>
> Normally, acpi_bus_trim keeps trimming as you say, and always returns the last
> error. Is this the desired behaviour that we want to keep for bus_trim? (This is
> more a general question, not specific to the eject_forbidden suggestion)
Your change makes sense to me. At least until we have rollback code in
place, we need to fail as soon as we hit an error.
> > Now, if acpi_bus_hot_remove_device() gets that error code, it should just
> > reverse the whole trimming (i.e. trigger acpi_bus_scan() from the device
> > we attempted to eject) and notify the firmware about the failure.
>
> sounds like this rollback needs to be implemented in any solution we choose
> to implement, correct?
Yes, rollback is necessary. But I do not think we need to include it
into your patch, though.
Thanks,
-Toshi
> > If we have that, then the memory hotplug driver would only need to set
> > flags.eject_forbidden in its .add() routine and make its .remove() routine
> > only clear that flag if it is safe to actually remove the memory.
> >
>
> But when .remove op is called, we are already in the irreversible/error-free
> removal (final removal step).
> Maybe we need to reset eject_forbidden in a prepare_remove operation which
> handles the removal part that can fail ?
>
> thanks,
>
> - Vasilis
next prev parent reply other threads:[~2012-11-29 18:04 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-23 17:50 [RFC PATCH v3 0/3] acpi: Introduce prepare_remove device operation Vasilis Liaskovitis
2012-11-23 17:50 ` [RFC PATCH v3 1/3] acpi: Introduce prepare_remove operation in acpi_device_ops Vasilis Liaskovitis
2012-11-27 0:10 ` Toshi Kani
2012-11-27 18:36 ` Vasilis Liaskovitis
2012-11-27 23:18 ` Rafael J. Wysocki
2012-11-23 17:50 ` [RFC PATCH v3 2/3] acpi_memhotplug: Add prepare_remove operation Vasilis Liaskovitis
2012-11-24 16:23 ` Wen Congyang
2012-11-23 17:50 ` [RFC PATCH v3 3/3] acpi_memhotplug: Allow eject to proceed on rebind scenario Vasilis Liaskovitis
2012-11-24 16:20 ` Wen Congyang
2012-11-26 8:36 ` Vasilis Liaskovitis
2012-11-26 9:11 ` Wen Congyang
2012-11-27 0:19 ` Toshi Kani
2012-11-27 18:32 ` Vasilis Liaskovitis
2012-11-27 22:03 ` Toshi Kani
2012-11-27 23:41 ` Rafael J. Wysocki
2012-11-28 16:01 ` Toshi Kani
2012-11-28 18:40 ` Rafael J. Wysocki
2012-11-28 21:02 ` Toshi Kani
2012-11-28 21:40 ` Rafael J. Wysocki
2012-11-28 21:40 ` Toshi Kani
2012-11-28 22:01 ` Rafael J. Wysocki
2012-11-28 22:04 ` Toshi Kani
2012-11-28 22:21 ` Rafael J. Wysocki
2012-11-28 22:16 ` Toshi Kani
2012-11-28 22:39 ` Rafael J. Wysocki
2012-11-28 22:46 ` Greg KH
2012-11-28 23:05 ` Rafael J. Wysocki
2012-11-28 23:10 ` Greg KH
2012-11-28 23:31 ` Rafael J. Wysocki
2012-11-28 23:49 ` Rafael J. Wysocki
2012-11-29 1:02 ` Toshi Kani
2012-11-29 1:15 ` Toshi Kani
2012-11-29 10:03 ` Rafael J. Wysocki
2012-11-29 11:30 ` Vasilis Liaskovitis
2012-11-29 16:57 ` Rafael J. Wysocki
2012-11-29 17:56 ` Toshi Kani [this message]
2012-11-29 20:25 ` Rafael J. Wysocki
2012-11-29 20:38 ` Toshi Kani
2012-11-29 21:23 ` Rafael J. Wysocki
2012-11-29 21:46 ` Toshi Kani
2012-11-29 22:11 ` Rafael J. Wysocki
2012-11-29 23:17 ` Toshi Kani
2012-11-30 0:13 ` Rafael J. Wysocki
2012-11-30 1:09 ` Toshi Kani
2012-11-29 16:43 ` Toshi Kani
2012-11-29 11:04 ` Vasilis Liaskovitis
2012-11-29 17:44 ` Toshi Kani
2012-12-06 9:30 ` Vasilis Liaskovitis
2012-12-06 12:50 ` Rafael J. Wysocki
2012-12-06 15:41 ` Toshi Kani
2012-12-06 20:32 ` Rafael J. Wysocki
2012-11-28 11:05 ` [RFC PATCH v3 0/3] acpi: Introduce prepare_remove device operation Hanjun Guo
2012-11-28 18:41 ` Toshi Kani
2012-11-29 4:48 ` Hanjun Guo
2012-11-29 22:27 ` Toshi Kani
2012-12-03 4:25 ` Hanjun Guo
2012-12-04 0:10 ` Toshi Kani
2012-12-04 9:16 ` Hanjun Guo
2012-12-04 23:23 ` Toshi Kani
2012-12-05 12:10 ` Hanjun Guo
2012-12-05 22:31 ` Toshi Kani
2012-12-06 16:47 ` Jiang Liu
2012-12-07 2:25 ` Toshi Kani
2012-12-06 16:40 ` Jiang Liu
2012-12-06 20:30 ` Rafael J. Wysocki
2012-12-07 2:57 ` Toshi Kani
2012-12-07 5:57 ` Jiang Liu
2012-12-08 1:08 ` Toshi Kani
2012-12-11 14:34 ` Jiang Liu
2012-12-13 14:42 ` Toshi Kani
2012-12-13 15:15 ` Jiang Liu
2012-12-15 1:19 ` Toshi Kani
2012-11-29 10:15 ` Rafael J. Wysocki
2012-11-29 11:36 ` Vasilis Liaskovitis
2012-12-06 16:59 ` Jiang Liu
2012-11-29 17:03 ` Toshi Kani
2012-11-29 20:30 ` Rafael J. Wysocki
2012-11-29 20:39 ` Toshi Kani
2012-11-29 20:56 ` Toshi Kani
2012-11-29 21:25 ` Rafael J. Wysocki
2012-12-06 17:10 ` Jiang Liu
2012-12-06 17:07 ` Jiang Liu
2012-12-06 17:01 ` Jiang Liu
2012-12-06 16:56 ` Jiang Liu
2012-12-06 16:00 ` Jiang Liu
2012-12-06 16:03 ` Toshi Kani
2012-12-06 16:25 ` Jiang Liu
2012-12-06 16:31 ` Toshi Kani
2012-12-06 16:52 ` Jiang Liu
2012-12-06 17:09 ` Toshi Kani
2012-12-06 17:30 ` Jiang Liu
2012-12-06 17:28 ` Toshi Kani
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